By adjusting volume of intake air at proper timings in response to rotation speed of an internal combustion engine and a load applied to the internal combustion engine and in response to an operational state of a device which is provided for the internal combustion engine, pulsating air particularly at low and middle speed ranges is increased, volumetric efficiency is increased to improve an engine output, intake flow velocity is increased to improve combustion, and smoke is reduced. A known air intake control apparatus includes a valve body (i.e., an air intake control valve) provided at the upstream of an intake valve and separately from the intake valve so that the air intake control valve opens and closes synchronously to an opening and closing of the intake valve in order to adjust the volume of the intake air. In those circumstances, the intake control valve is required to operate quickly in response to an operational state of an internal combustion engine. JPH08-218906A discloses an air intake control apparatus which includes a clearance provided between an air intake control valve and an inner wall of an intake passage. With the construction of JPH08-218906A, the air intake control valve opens and closes quickly while preventing a contact of the air intake control valve and the inner wall of the intake passage.
Considering isolation properties of the intake passage when the air intake control valve is fully closed, it is preferable that the clearance between the air intake control valve and the inner wall of the air flow passage is as small as possible. However, according to the known air intake control apparatus, generally, configurations and/or materials of members which construct the intake passage, a shaft body, and the air intake control valve are different. Thus, degree of expansion and contraction of each of the members in response to a change of temperature varies, and a relative position between the inner wall of the intake passage and the intake valve varies in response to the change of the temperature. Accordingly, with the construction of the known air intake control apparatus, in order to prevent a contact of the inner wall of the intake passage to the valve body, it is necessary to provide a large degree of the clearance.
A need thus exists for an air intake control apparatus which is not susceptible to the drawback mentioned above.